Prognosis of CKD patients receiving outpatient nephrology care in Italy

Abstract

Background and objectives: Prognosis in nondialysis chronic kidney disease (CKD) patients under regular nephrology care is rarely investigated. Design, setting, participants, & measurements We prospectively followed from 2003 to death or June 2010 a cohort of 1248 patients with CKD stages 3 to 5 and previous nephrology care ≥1 year in 25 Italian outpatient nephrology clinics. Cumulative incidence of ESRD or death before ESRD were estimated using the competing-risk approach.

Results: Estimated rates (per 100 patient-years) of ESRD and death 8.3 (95% confidence interval [CI], 7.4 to 9.2) and 5.9 (95% CI 5.2 to 6.6), respectively. Risk of ESRD and death increased progressively from stages 3 to 5. ESRD was more frequent than death in stage 4 and 5 CKD, whereas the opposite was true in stage 3 CKD. Younger age, lower body mass index, proteinuria, and high phosphate predicted ESRD, whereas older age, diabetes, previous cardiovascular disease, ESRD, proteinuria, high uric acid, and anemia predicted death (P < 0.05 for all). Among modifiable risk factors, proteinuria accounted for the greatest contribution to the model fit for either outcome.

Conclusions: In patients receiving continuity of care in Italian nephrology clinics, ESRD was a more frequent outcome than death in stage 4 and 5 CKD, but the opposite was true in stage 3. Outcomes were predicted by modifiable risk factors specific to CKD. Proteinuria used in conjunction with estimated GFR refined risk stratification. These findings provide information, specific to CKD patients under regular outpatient nephrology care, for risk stratification that complement recent observations in the general population.

Figure 1.

Prevalence of uncontrolled risk factors (as defined in the Study Population and Methods section) in CKD stages 3 (white), 4 (light gray), and 5 (dark gray). The bars show 95% confidence interval values. The P values for trends across stages are as follows: P = 0.69 for hypertension, P < 0.001 for proteinuria, P = 0.27 for high cholesterol, P = 0.05 for hyperuricemia, P < 0.001 for anemia, P = 0.12 for high phosphate, and P = 0.12 for smoking.

Figure 2.

Cumulative incidence of ESRD, death before ESRD, and the composite outcome (first occurrence of ESRD or death) stratified by chronic kidney disease stage. A competing risk approach was used to evaluate the extent to which the cumulative probabilities of the overall composite end point reflected ESRD or death during follow-up. The number of patients at risk refers to the composite end point.

Figure 3.

Plots of adjusted hazard ratios and 95% confidence intervals (as indicated by the curvilinear dash lines; the horizontal dash lines represent HR1) for ESRD in the three CKD stages and death for all stages by level of proteinuria as continuous variable (reference level, 0.5 g/24 h).